Wireless LANs (local area networks) are emerging as important infrastructure for a wide range of commercial and domestic premises. They enable mobility of wireless devices about the premises and are generally more flexible and lower cost than networks with equivalent wired connections. However, a large number of wireless access points may be required to properly serve the coverage volume of a particular network, and different mobile devices may require service within the volume using different wireless protocols. This increases the number of wireless interface controllers with RF (radio frequency) transceivers that are required by the network, and therefore increases its cost. Distributed access points having a number of relatively simple cells or POPs (points of presence) for transmission and reception of RF signals are therefore under development. Each access point has a central server with a set of transceivers that are typically connected to the POPs by optical fibres, coaxial cables or the like, through a bridge or switch.
Diversity techniques can improve wireless communication by selecting one channel, or combining a subset of channels, from a range of decorrelated channels that may exist between a transmitter and a receiver. A range of different algorithms exist for selecting or combining signals from among the available channels. In spatial diversity each channel is a physical path between a transmitting antenna and a receiving antenna, with selection of the most suitable receiving antenna according to analysis of the respective signal. Macro diversity counters large scale and generally static spatial variations between the receiving antennae such as shadowing. Micro diversity counters relatively small scale and often time varying effects such as multipath fading. Both macro and micro spatial effects can be important in wireless LANs with distributed access points.